The invention is based on an internal combustion engine with externally-supplied ignition. In known internal combustion engines of this kind, if they are operated with a fuel-air mixture which is kept as lean as possible or with a conventional fuel-air mixture where a relatively large quantity of recirculated exhaust gas is present, and this mixture must be externally ignited, then there is the danger that the mixture may ignite poorly. In order to attain both satisfactory, reliable ignition and the reaction of the fuel and air with one another while the fuel component is as small as possible, attempts have been made in various ways, having generally to do with attaining a mixture enrichment close to the ignition location in an ignition chamber by means of layering. By increasing the temperature level of the mixture at the ignition location and by taking measures which effect the greatest possible freedom from residual gas on the part of the mixture to be ignited, a high degree of fuel-air mixture leaning can also be attained, while providing both a favorable exhaust gas composition and good utilization of the fuel.
In a known embodiment, the middle and ground electrodes of the ignition apparatus are carried directly up to the inside discharging point of the overflow channel, so that the ignition spark is created directly in the highly turbulent flow region of the inflowing fresh mixture made up of fuel and air. This position for the electrodes has the advantage, on the one hand, of a high degree of freedom from residual gas on the part of the mixture to be ignited and, on the other hand, of a high temperature level at the ignition location. The ignition reliability of this apparatus is thus very great; however, the service life of such electrodes is quite short, because of the thermal stress imposed by the combustion gases flowing in and out (see German Offenlegungsschrift No. 25 03 811).